Concrete structures can undergo accelerated deterioration due to corrosion of the reinforcing steel rods. The corrosion is caused by the gradual introduction of chloride into the concrete from deicing salts. Applying penetrating sealers can greatly diminish the intrusion of chloride into the concrete.
Solutions of alkyltrialkoxysilanes in organic solvents have been used very effectively to impart water repellent properties to porous masonry substrates such as mortar and concrete. These formulations penetrate the masonry substrate and provide a significant hydrophobic layer. However, solvent base formulations are undesirable due to the large amount of volatile organic components that are released into the air during their use. Various state regulations prohibit the volatile organic content (VOC) of an architectural coating from exceeding four hundred grams per liter.
The prior art solvent base coatings have not met these regulations. To reduce the amount of organic compounds released into the air, preparations of aqueous emulsions of alkyltrialkoxysilanes have been reported.
The utility of silanes in such aqueous emulsions, especially alkoxysilanes, as masonry water repellents is a widely known use because of their hydrophobic nature. For example, U.S. Pat. No. 4,648,904 issued to DePasquale and Wilson teaches a porous masonry water repellent composition comprising: a hydrolyzable silane, an emulsifying agent and water. U.S. Pat. No. 4,877,654 issued to Wilson teaches a similar composition but also contains a buffering compound to maintain the composition within the pH stable range. U.S. Pat. No. 5,074,912, issued to Liles and Klein also teaches a water repellent composition for treating porous substrates consisting of an emulsion containing water, at least one surfactant, and a siloxane. However, the emulsifiers taught therein are generally nonionic surfactants and only one type of silane (the active ingredient) may be used at a time in each emulsion. It has been found that nonionic emulsifiers, in particular highly ethoxylated surfactants, reduce the hydrophobic effect of these compositions. This leads to an increase in water absorption of the masonry material and in most cases a reduction in penetration depth of the silane.
Another example of prior art aqueous emulsions is taught in U.S. Pat. No. 4,433,013 issued to Puhringer, which discloses a water-sealant for inorganic porous mineral substrates which comprise an emulsion of at least one silane, one deactivatable surfactant, an organic alcohol, and water. The surfactants taught as useful therein include fatty acid esters, and particularly alcohol/alkylene oxide adducts.
Moreover, in unrelated fields, the manufacture and use of quaternary ammonium pendant siloxane copolymers have been known. See U.S. Pat. No. 4,895,964, issued to Margida. The uses in the prior art of such quaternary polylsiloxanes have been in cosmetic preparations, as disclosed in the U.S. Pat. No. 4,891,166, issued to Shaefer and Krakenberg and in waterproofing compositions with good fungitidal and mildewcidal properties, as disclosed in European Patent Application, Publication No. 0,469,624, to Yoshioka.